Ken Goldin of Goldin Auctions said it is one of the rings that Brady authorized to have made after last year's title. It was consigned by its owner, who has chosen to remain anonymous.

The championship team pays for the players' rings, but players can authorize friends and family to purchase rings that look almost identical.

One of the Super Bowl LI rings Tom Brady authorized to have made after last year's title is up for auction. Goldin Auctions

The Brady ring being auctioned has 260 diamonds compared to the one Brady and the other New England Patriots players received from the team, which has 283 diamonds each. Goldin said the auctioned ring is about 10 percent smaller than Brady's, though it does have the same engraving.

The winner of the auction will get the insurance certificate prepared by the ring's maker, Jostens, for Brady. The value of the ring is $29,700 on gemstones and gold alone.

The auction ends Feb. 17.

"This is the first Brady award that has ever come to market," Goldin said. "He never lets things go, and nobody from his inner circle has ever given up something like this."

Brady is known to cherish his own memorabilia. His missing Super Bowl LI jersey led to a police and FBI investigation that resulted in its recovery from a journalist from Mexico.

Goldin said he expects the ring to easily be a six-figure item. In 2013, Goldin sold a Los Angeles Lakers 2000 championship ring that Kobe Bryant gave to his father for $173,102.

One actual Super Bowl LI player ring has been sold. SCP Auctions founder David Kohler told ESPN he sold one in a private sale for $75,000. He said he could not disclose the player's name.